#include <iostream>
using namespace std;

namespace zty{
  int a = 0;
  void printa(int val = a){
    cout << val << endl;
  }
}

int main(){
  //for(int i = 0; i<10; ++i)
  //{
  //  zty::printa();
  //  ++zty::a;
  //}
  cout << sizeof(nullptr) << endl;
  cout << sizeof(NULL) << endl;
  cout << sizeof(0) << endl;
  cout << sizeof((void*)0) << endl;
}
